Authors

Abstract

To address the problems of unstable posture, end crushing, and poor release during conventional press-in sand barrier laying caused by the large diameter, rigid internodes, pronounced nodes, and heterogeneous structure of corn stalks, a smooth composite insertion pin consisting of a front steel pin and a rear sleeve was designed. Based on the structural characteristics of the corn stalk rind, pith, and nodes, a layered discrete element model was established to analyze pith compression, sidewall friction, and local failure during axial insertion. The sleeve contact-segment diameter, steel pin diameter, and sleeve front transition angle were selected as experimental factors, and insertion force stiffness was adopted as the evaluation index. A Box-Behnken response surface design was employed for parameter optimization, followed by internodal validation, finite element analysis, nodal insertion tests, and release tests. The results showed that the sleeve contact-segment diameter had the greatest influence on insertion force stiffness, while the steel pin diameter and transition angle also had significant effects. The regression model exhibited a good fit, and the lack-of-fit was not significant. Considering machining feasibility and structural stability, the optimal structural parameters were a sleeve contact-segment diameter of 5.5 mm, a steel pin diameter of 2.0 mm, and a sleeve front transition angle of 160°, corresponding to a predicted insertion force stiffness of 1.15 N/mm. The validation results agreed well with the model predictions. Although the insertion force increased substantially in the nodal region, the optimized composite insertion pin successfully achieved axial insertion through the nodes and enabled smooth release in both the internodal and nodal regions.

Abstract in Chinese

针对玉米秸秆直径大、节间硬、结节明显及组织非均质导致传统压入式沙障铺设中姿态不稳、端部压溃和脱落不畅等问题，设计了“前端钢针+后部套筒”的光滑复合插针。基于玉米秸秆表皮、内瓤和结节结构特征，建立分层复合离散元模型，分析轴向插入中的内瓤压缩、侧壁摩擦和局部破坏行为。以套筒接触段直径、钢针直径和套筒前端变径角为因素，以插入力刚度为评价指标，开展 Box-Behnken 响应面优化，并通过有限元分析、结节插入和脱落试验进行验证。结果表明，套筒接触段直径影响最显著，钢针直径和变径角也具有显著影响。推荐参数为 5.5 mm、2 mm 和 160°，预测插入力刚度约为 1.15 N/mm。验证结果表明，结节处插入力明显升高，但优化后复合插针仍可完成结节处轴向插入，并能在普通节间和结节位置顺利脱落。